1. Field of the Invention
The present invention relates to a stent that can be used to maintain flow in ducts in the body and, more particularly, to a stent for biliary drainage in patients whose biliary channels are obstructed for example due to cancer or benign disease.
2. Description of the Related Art
There are at least 4,000 new cases of biliary cancer, and more than 25,000 cases of pancreatic cancer every year, and the incidence appears to be rising. These cancer present with jaundice, due to obstruction of the bile duct. Unfortunately, by the time this stage is reached the tumor is usually at an advanced stage and unresurrectable. Management at this stage, therefore, usually consists of palliation only.
Although surgical bypass procedures are effective for palliative purposes, most patients with these cancers are either too sick to undergo major surgery or have too short a life-span to make the operation worthwhile. For this reason, palliation of jaundice in these biliary cancers is most often done by the endoscopic insertion of a biliary stent or endoprosthesis across the obstructed area. These are of two types: 1) plastic, and 2) expandable metal stents. Both types of conventional stents have problems associated with their use. Conventional plastic stents tend to clog with debris and biofilm relatively early. Metal stents overcome this problem by providing a greater initial lumen but also tend to clog, in their case with tumor ingrowth. Also, metal stents are extremely expensive, about 20 times more expensive than plastic stents. Even further, the metal stents are technically more difficult to insert and once in place, can not be removed.